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Musculoskeletal Function
can be regarded not as a single disease but as a category
of disorders, all involving chronic (long-term) joint
inflammation, that begins before a child reaches the
age of 16 and lasts for 6 weeks to 3 months. It may be
present as an oligoarticular disorder (involving less than
5 joints) or as a polyarticular disorder (involving 5 or
more joints), and may include other systemic manifesta-
tions such as fever, rash, and/or eye inflammation.
The initial symptoms of JIA may be subtle or acute,
and often include morning stiffness and gelling; easy
fatigability, particularly after school; and joint swelling.
The involved joints are often warm, resist full range of
motion, and are painful on motion, but not erythema-
tous.
71
Oligoarthritis
, which is the most common type of
JIA, predominantly affects joints of the lower extremi-
ties, usually the knees or ankles. Involvement of upper
extremity large joints and the hip is rarely a present-
ing sign. Often a single joint is affected at onset. The
severity of joint symptoms is usually mild, and it is not
uncommon for children to present with normal or near-
normal overall function. Children with this form of
JIA are usually younger (1 to 5 years at onset), more
likely to be girls (girls outnumber boys by 4 to 1), often
rheumatoid factor (RF) positive (discussed under rheu-
matoid arthritis), and at greater risk for developing
chronic eye inflammation.
70
The inflammation primarily
involves the anterior chamber of the eye and is associ-
ated with minimal, if any, symptoms in about 80% of
cases. Because severe eye changes can occur, these chil-
dren should be screened at regular intervals and treated
by an experienced eye specialist.
The
polyarticular
form of the disorder is generally
characterized by involvement of both large and small
joints. This form of JIA may develop at any age up to 16
years of age, with girls outnumbering boys by 3 to 1.
70
This form of arthritis more closely resembles the adult
form of the disease than the other two subgroups. The
RF sometimes is present and may indicate a more active
disease process. Clinical manifestations are highly vari-
able and include fatigue, low-grade fever, weight loss,
malaise, anemia, stunted growth, slight organomegaly
(e.g., hepatosplenomegaly), and lymphadenopathy.
Systemic-onset disease
, which affects approximately
2% to 17% of children with JIA, is characterized by
arthritis and prominent visceral involvement that include
hepatosplenomegaly, lymphadenopathy, and inflamma-
tion of serous membranes, such as in pericardial effu-
sion.
70
The symptoms of systemic JIA include a daily
intermittent high fever, which usually is accompanied by
a characteristic faint, erythematous, macular rash. The
salmon-colored lesions of the rash may be linear or cir-
cular, from 2 to 5 mm in size, and appear in groups with
a linear distribution on the trunk and proximal extremi-
ties. The rash is not pruritic (it does not cause itching).
The most prominent diagnostic feature is its transient
nature, with a group of lesions lasting less than an hour.
Systemic symptoms usually subside in 6 to 12 months.
The prognosis for most children with JIA is good.
NSAIDs are the first-line drugs used in treating JIA.
Most children with polyarticular or systemic JIA,
however, need additional anti-inflammatory therapy.
74
Corticosteroids are recommended only for overwhelm-
ing inflammation of systemic disease. Disease-modifying
antirheumatic drugs (DMARDs), such as methotrexate,
may also be used. Careful attention to growth and devel-
opment and nutritional issues are additional aspects of
treatment of children with JIA. Children are encouraged
to lead as normal a life as possible.
Juvenile Spondyloarthropathies
Ankylosing spondylitis, reactive arthritis, psoriatic
arthritis, and spondyloarthropathies associated with
ulcerative colitis and regional enteritis can affect chil-
dren as well as adults.
75–78
The arthropathies of inflam-
matory bowel disease and reactive arthritis are much
less common in childhood.
75
In children, spondyloarthropathy manifests in
peripheral joints first, mimicking pauciarticular JIA,
with no evidence of sacroiliac or spine involvement for
months to years after onset. The spondyloarthropa-
thies are more common in boys and commonly occur in
children who have a positive family history. HLA-B27
typing is helpful in diagnosing children because of the
unusual presentation of the disease. Juvenile ankylosing
spondyloarthritis frequently begins with oligoarthritis
and enthesitis or inflammation at the site where muscles
insert into bone. The arthritis occurs predominantly in
the lower extremities and frequently involves the hips.
75
Enthesitis is particularly common, manifesting as local
and often severe tenderness over involved tendons and
ligaments, especially those around the plantar surface of
the foot, ankle, and knee. The disease course is variable
and can include periods of low and high disease activity.
Juvenile psoriatic arthritis is composed of two sub-
groups, differentiated by age of onset. Older children
have features of spondyloarthritis, including a relative
male preponderance, increased risk of axial involve-
ment, and enthesitis.
76
The mechanisms appear to
involve autoinflammatory dysregulation centered at the
synovial-entheseal complex. In contrast, children with
early-onset disease bear similarities to children with
early onset oligoarticular and polyarticular JIA disor-
ders, including a female preponderance and positive
RF factor, suggesting a possible role for autoimmune
mechanisms. Inflammation of the fingers is seen in both
groups, however.
Management of the disease involves physical therapy,
education, and attention to growth and developmental
issues.
77,78
Medication includes the use of salicylates or
other NSAIDs. In children who are not responsive to
these medications, sulfasalazine or methotrexate may
be considered. Exercises to maintain range of motion of
the back, thorax, and affected joints should be instituted
early in the disease. Custom-fitted shoes are particularly
useful in managing painful entheses of the feet.
75
Juvenile Dermatomyositis
Juvenile dermatomyositis (JDM) is a rare, presumably
autoimmune disorder that causes proximal muscle
weakness and a characteristic rash.
79–81
The disorder can
affect children of all ages, with an average age at onset
